Estudo da expansão por umidade e de características cerâmicas correlatas de placas cerâmicas para revestimento.

Abstract

The ceramic tile sector has showing high increasing indexes in the last years, what ratify the position of Brazil as one of the principal world producer and great exporter, in potential. Although this increasing came with a raised demand by better quality, making necessary more research on ceramic tiles. Thus, this work has as aim study the moisture expansion and correlated ceramic characteristics (water absorption, crazing-resistance and thermal expansion) of ceramic tiles, according the ABNT standardization, and try to determine inter-relations between these properties. Were bought twenty tree samples of nineteen commercial brands of ceramic tiles in the market of Campina Grande - PB that are originated from plants of the northeastern and southeastern states. Afterwards were did tests to determine the water absorption, thermal expansion, crazing-resistance and moisture expansion, all of them according to the NBR 13818 norm. Based in the results can be concluded that: the great majority of the ceramic tiles studied were in the class of the semiporous materials, with absorption between 6-10%; around 30% of the tiles had crazes after the crazing-resistance test; the majority of the tiles had moisture expansion, after boiling, between 0,0% and 0,03%, being indicated in the NBR 13818 norm that expansions above 0,06% may contribute to problems in the tiles service, the boiling seem to cause an kind of erosion in the test samples during the test to determine the moisture expansion; the analyze using phase diagrams indicated that the studied tiles have a decreasing relation between the water absorption and the estimated quantity of glass phase, and a decreasing behavior between the moisture expansion, after boiling, and the estimated quantity of glass phase and that the obtained values of the linear thermal expansion coefficient were situated in the range of 6 to 8 x 10"6 °C"', being indicated in the EN 103 norm, that the these values have to be inferiors to 9 x 10"6 °C"1, when the ceramic tiles are processed by pressing.